Alpha + beta or beta TITANIUM ALLOY AND METHOD FOR PRODUCTION THEREOF

ABSTRACT

A titanium alloy containing copper, which cannot be realized by a conventional method, is provided, having a composition in which copper is contained in titanium with no segregation, and having improved strength and hardness. In addition a method is also provided, in which the titanium alloy is produced at lower cost than in a conventional method. The α+β or β titanium alloy contains copper at 1 to 10 mass %, has a crystal phase of β and α phase or of β phase, is formed of crystal particles not more than 100 μm, and has a copper concentration per an arbitrary specified 1 mm 3  portion of the crystal phase at within ±40% compared to another arbitrary specified portion. The α+β or β titanium alloy is produced by mixing 1 to 10 mass % of copper powder and the remainder of titanium alloy powder and then pressing and forming while being heated. The method for production of the α+β or β titanium alloy has a step of mixing 1 to 10 mass % of copper powder and the remainder of titanium alloy powder and a step of pressing and forming the mixture while being heated.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser. No. 14/113,823 filed Oct. 25, 2013, which is a 371 of International Application No. PCT/JP2012/061782, filed Apr. 27, 2012, which claims priority to JP 2011-099116, filed Apr. 27, 2011, the contents of each of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to titanium alloys, and in particular, relates to a titanium alloy which has superior mechanical properties, such as strength and hardness, compared to Ti-6Al-4V alloys or the like, and has a composition that cannot be produced by a conventional melting method, and relates to a method for production of the titanium alloy in which the alloy is produced at low cost.

BACKGROUND ART

Recently, the demand for titanium alloys has greatly increased due to recent increase in the application fields, not only in the aircraft industry, but also in the field of consumer use. In particular, since high quality and various functions are required in alloys for aircraft use, high quality is the most important criteria, and in many cases, production cost reduction is the secondary one.

However, the effort of production cost reduction for titanium alloys would result in the increase of the amount used of light titanium alloys from a viewpoint of energy conservation of production processes of alloys and improvements in yields, that is, it would result in energy load reduction of operation of machines, and they would be considered to satisfying the needs of society.

In particular, Ti-6Al-4V alloy (hereinafter simply referred to as 64 alloy) has been conventionally used in the aircraft industry since it has superior mechanical properties. However, there is one problem in that the 64 alloy is difficult to be assembled in complicated structure parts since it has inferior workability.

In view of such circumstances, Ti-4.5Al-3V-2Fe-2Mo alloy (so called “SP700”) has been developed in order to improve workability of the 64 alloy. Furthermore, Ti-10V-2Fe-3Al (so called “10-2-3 alloy”), Ti-15V-3Cr-3Al-3Sn (so called “15-3-3-3-3 alloy”) or the similar alloy has been developed in which strength is further improved while maintaining the 64 alloy elongation level. However, vanadium, iron or the similar element is easily segregated in any of the alloys SP700, 10-2-3, 15-3-3-3-3, therefore further improvement has been required.

Non-patent document 1 below discloses that workability of titanium material can be further improved by adding more than 1 wt % of copper to pure titanium. However, it is difficult to add more than 1% to titanium since copper would be segregated greatly in titanium. Therefore, there is a limitation of further improvement in above properties of the alloys, and the problem remains to be solved.

On the other hand, a “raw powder mixing method” is known (see below patent document 1 and non-patent document 2) in which the 64 alloy is produced using metallic powder. The raw powder mixing method is known in that each element powders required for alloy are prepared independently, and these powders are uniformly mixed to form complex powders, and the complex powders are used for raw materials of titanium alloys.

However, although the raw powder mixing method is promising on a laboratory scale experiment, there are big hurdles to overcome the cost reducing solution in the actual production scales, and the raw powder mixing method is merely in practical use, and moreover, there is no report of production of titanium alloy containing copper in high concentration.

The cost of titanium powder should depend on the high price of pure titanium raw material, and further improvement is required for reducing the cost of titanium powder.

Titanium alloys having mechanical properties superior to those of the 64 alloy are desired, and a method of producing the low cost alloys are desired as explained.

-   Patent document 1: Japanese Unexamined Patent Application     Publication No. Hei05 (1993)-009630 -   Non-patent document 1: Material, Vol. 48 (2009), (11), pp. 547-554,     by Fujii, Takahashi, Mori, Kawakami, Kunieda and Otsuka -   Non patent document 2: Toyota Central Institute R&D Review Vol. 29     (1994), (3), pp. 49-60, by Saito and Furuta

SUMMARY OF THE INVENTION

As is explained, an object of the present invention is to provide titanium alloy containing copper with no segregation, which cannot be realized by a conventional method, and having improved strength and hardness. In addition, another object is to provide a method for producing the copper containing titanium alloy at lower cost than a conventional one.

The inventors have researched in view of the above circumstances, and they have found that titanium alloy having superior strength, elongation and hardness compared to a conventional method can be produced by using a metallurgical powder method to produce titanium alloy, rather than a melting method, by producing titanium alloy powder while employing a hydrogenation-dehydrogenation method on raw titanium alloy, and furthermore, by mixing the titanium alloy powder and copper powder and then pressing and forming this mixed powder while being heated, and thus the present invention has been completed. Here, in the present invention, “pressing and forming while being heated” means that mixed powder in which copper powder is added to titanium powder is pressed and formed under warm or hot conditions.

As a result, they found that a titanium alloy containing copper in high concentration, which has been difficult to produce by conventional methods, can be produced, and that titanium alloy having a uniform structure and few segregations of copper can be produced in the reasonable cost range, and the present invention was completed.

Furthermore, a titanium alloy produced by the method above mentioned not only has higher strength due to low segregation of alloy components, but also has superior hardness compared with a titanium alloy produced by the conventional method.

That is, an α+β or β titanium alloy of the present invention contains copper in a range of 1 to 10 mass %, crystal phase of the alloy is β phase or is α and β phase, the crystal particle size in β phase or is α and β phase is not more than 100 μm, and copper concentration per 1 mm³ of arbitrary specified portion in the crystal phase is within ±40% compared to another arbitrary specified portion.

Furthermore, it is desirable that the α+β or the β titanium alloy according to the present invention is obtained by mixing copper powder and titanium alloy powder prepared independently, and then pressing and forming the mixed powder while being heated.

Furthermore, in the α+β or the β titanium alloy according to the present invention, it is desirable that the titanium alloy powder is produced by titanium alloy as a raw material, and the titanium alloy contains at least one kind selected from aluminum, vanadium, molybdenum, iron, chromium, and tin.

A method for production of the α+β or the β titanium alloy of the present invention is a production method of the α+β or the β titanium alloy containing copper, and includes a step in which 1 to 10 mass % of copper powder and titanium alloy powder are pressed and formed while being heated so as to form dense compact.

In the method for production of the α+β or β titanium alloy according to the present invention, it is desirable that temperature in the pressing and forming while being heated (Tw(° C.)) is employed in the range of (Td−100° C.)<Tw<(Td+100° C.), and in this case, Td(° C.) means β transformation temperature of titanium alloy which is pressed and formed.

Furthermore, in the method for production of the α+β or the β titanium alloy according to the present invention, it is desirable that the titanium alloy powder is produced from titanium alloy as a raw material, and the titanium alloy contains at least one kind selected from aluminum, vanadium, molybdenum, iron, chromium, and tin.

By the method for production of the α+β or β titanium alloy according to the present invention mentioned above, titanium alloy containing copper at high concentration, having structure with no segregation of copper, and having strength and hardness, which cannot be produced by a conventional method, can be produced in the reasonable cost range.

As a result, the titanium alloy according to the present invention can be appropriately employed to fields of high-strength mechanical parts, medical materials, and aircraft materials.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a flowchart diagram showing the method for production of the α+β or β titanium alloy according to the present invention.

FIGS. 2A and 2B are microscope photographs showing structures of sintered bodies of examples; FIG. 2A is the sintered body of Example 2-1, and FIG. 2B is the sintered body of Example 2-2.

FIGS. 3A, 3B, 3C and 3D are EPMA images showing distribution of elements of Ti, V, Al, and Cu in an Example.

BEST MODE FOR CARRYING OUT THE INVENTION

The best mode for carrying out the present invention is explained with reference to the drawings.

The α+β or β titanium alloy according to the present invention contains copper in a range of 1 to 10 mass %, crystal phase of the alloy is β phase or is a phase and (3 phase, the crystal phase consists of crystal particles not more than 100 μm, and copper concentration per 1 mm³ of an arbitrary specified portion in the crystal phase is within ±40% compared to another arbitrary specified portion.

In a conventional powder metallurgical method, due to addition of copper powder to alloy powder, which is produced using titanium alloy as a raw material, there may be a case in which differences of concentration are generated among multiple portions that are mutually different in an alloy. However, in the titanium alloy according to the present invention, since copper concentration per 1 mm³ of an arbitrary specified portion in the crystal phase is reduced to within ±40% compared to another arbitrary specified portion, the overall alloy structure is maintained sufficiently uniform.

Furthermore, the α+β-type or β-type titanium alloy according to the present invention is produced by a method in which titanium alloy powder containing copper powder in a range from 1 to 10 mass % is pressed and formed while being heated.

Here, in the present invention, “titanium alloy powder containing copper powder in a range of 1 to 10 mass %” means complex powder in which copper powder separately prepared is added and mixed to titanium alloy powder not containing copper powder.

In the present invention, as the titanium alloy powder, it is desirable to use titanium alloy powder containing aluminum or vanadium. As a desirable example of such an alloy powder, Ti-6Al-4V alloy powder, Ti-3Al-2.5V alloy powder or the like may be mentioned.

In addition to aluminum or vanadium, alloy powder containing molybdenum, iron, chromium, or tin may be mentioned. Typical alloy powders of these may be mentioned as follows.

Ti-10V-2Fe-3Al alloy powder, Ti-15V-3Al-3Al-3Cr-3Sn alloy powder, Ti-4.5Al-3V-2Fe-2Mo alloy powder, Ti-5Al-5V-5Mo-3Cr alloy powder, and Ti-5Al-4V-0.6Mo-0.4Fe alloy powder.

It is desirable that the above-mentioned titanium alloy powder is produced by a hydrogenation-dehydrogenation method (hereinafter simply referred to as an HDH method) using cut chips or cut powder or scraps of ingots as a raw material.

FIG. 1 shows a preferable embodiment of a process for production of titanium alloy according to the present invention. As a raw material for titanium alloy supplied to the present invention, alloy scraps or titanium alloy ingots which originally had desirable components, such as titanium alloy cut powder, titanium alloy forged pieces, edge materials of titanium alloy rods or the like can be mentioned.

By using the alloy scrap material as a raw material, production costs of the titanium alloy powder can be effectively reduced. It is desirable that these titanium alloy scraps or titanium alloy ingots (hereinafter simply referred to as “titanium alloy raw material”) be adjusted beforehand within a predetermined length or size.

For example, it is desirable to cut beforehand to a length not more than 100 mm in a case of alloy cut powder. By cutting to such a length, a hydrogenation process, which is the next process, can be efficiently promoted. Furthermore, in a case of forged chips, which are block shaped alloy scraps, it is not particularly necessary for it to be processed beforehand, as long as it has size that can be placed in a hydrogenation furnace. It is desirable to be cut into powder in a case in which the raw material is titanium alloy ingots.

As mentioned above, the titanium alloy raw material, which is modified is provided to the hydrogenation treatment process under a hydrogen atmosphere. It is desirable that the hydrogenation treatment be performed in a temperature range of 500 to 650° C. Since the hydrogenation treatment reaction of the alloy raw material is an exothermic reaction, any operation to increase temperature is not necessary along with promoting of the hydrogenation reaction, and the hydrogenation reaction can be promoted spontaneously.

It is desirable that the titanium alloy raw material, which has been treated by hydrogenation treatment (hereinafter simply referred to as “hydrogenated titanium alloy”), be cooled to room temperature, and then be ground and sieved under an inert gas atmosphere such as argon gas, so as be of predetermined particle size.

Then, it is desirable that the hydrogenated titanium alloy powder that has been ground and sieved in powder shape be heated up to a high temperature range under a reduced pressure atmosphere.

It is desirable that the dehydrogenation treatment be performed in a temperature range of 500 to 800° C. while evacuating the atmosphere to form a vacuum. Since the dehydrogenation reaction is an endothermic reaction, which is the opposite to the above-mentioned hydrogenation treatment reaction, heating operation is necessary until hydrogen is no longer generated from the hydrogenated titanium alloy powder.

The titanium alloy powder according to the present invention can be obtained by the abovementioned operation. It is desirable that the titanium alloy powder of the present invention be adjusted in its particle size so as to be in a range from 1 to 300 μm, and more desirably from 5 to 150 μm. There may be a tendency for it to be difficult to increase the densities of alloys in final products if the particle diameter is rougher than this range, but on the other hand, undesirably, bulk density may be decreased, it may become easily oxidized, content of oxygen may be increased, and it may easily burn if finer than this range.

There may be a case in which the titanium alloy powder obtained by finishing the dehydrogenation treatment is sintered. In this case, it is desirable to perform breaking and grinding if necessary.

In the present invention, copper powder of 1 to 10 mass % is added to the titanium alloy powder produced by the above method.

By adding copper powder from 1 to 10 mass % to the titanium alloy powder produced, strength and hardness of the titanium alloy material, which is obtained by pressing and forming using the above alloy powder as a raw material, can be maintained in high level.

It is desirable that the particle size of copper powder to be added to the titanium alloy powder be adjusted to be in a range from 1 to 300 μm. Copper powder in a range of 1 to 50 μm is more desirably used.

Since the finer the copper powder, the more advantageous it is in the production of titanium alloy powder having uniform composition, it is desirable that the average particle size of the copper powder (d50) be adjusted in a range of 10 to 40 μm, in the range of particle size of 1 to 50 μm mentioned above.

In the present invention, it is desirable that the copper-added titanium alloy powder obtained by the above method be mixed uniformly, and then be pressed and formed while being heated.

As a pressing and forming method performed in the present invention, a conventional technique such as HIP, hot pressing, CIP-HIP, Hot-extrusion or the like can be employed, and in particular, the Hot-extrusion is superior from a viewpoint of productivity since sintering and shape forming are simultaneously promoted in a short time.

In the present invention, it is desirable that the titanium alloy powder in which copper powder is mixed be filled in metallic capsule and then be pressed and formed while being heated.

Titanium alloy material which is obtained by extrusion of titanium alloy powder in which copper powder is mixed and which is filled in the metallic capsule is a titanium alloy containing copper of high composition which could not be produced by a conventional method, exhibiting small segregation of copper, and exhibiting the superior mechanical properties of being strong and hard.

It is desirable that temperature (Tw) of pressing and forming mentioned above be in a range of (Td−100° C.)<Tw<(Td+100° C.). Here, Td means β transition temperature of titanium alloy, which is an objective of pressing and forming By heating the titanium alloy powder beforehand to be in the above range, the above-mentioned pressing and forming can be smoothly promoted.

In a case in which the temperature of pressing and forming is lower than (Td−100° C.), deformation resistance of titanium alloy becomes great, and it may be difficult to maximally densify the titanium alloy powder after pressing and forming. In particular, in a case in which pressing and forming are performed by extrusion, there may be a case in which raw material undesirably clogs up in a die.

On the other hand, in the present invention, in a case in which the temperature of pressing and forming is higher than (Td+100° C.), there may be a tendency for crystal particles of titanium alloy material to be more coarse than 100 μm, and mechanical properties of a titanium alloy material may be undesirably adversely affected.

Furthermore, in the present invention, in a case in which the temperature of pressing and forming is between (Td−100° C.) and Td, that is, pressing and forming is performed in the α+β region, and since crystal structure of titanium alloy material after pressing and forming is uniform and fine, it is not only strong and hard, but also exhibits superior mechanical properties which has a good balance of tensile strength and elongation.

The titanium alloy according to the present invention is characterized in that the content of copper composition is 1 to 10 mass %, and copper concentration per 1 mm³ of an arbitrary specified portion in the alloy is within ±40% compared to copper concentration in another arbitrary specified portion.

The abovementioned aspect means that copper is distributed almost uniformly in the titanium alloy according to the present invention.

Among titanium alloys having such a structure, in particular, as exemplified by the Ti-6Al-4V alloy, tensile strength is from 1400 to 1550 MPa, and elongation is from 2 to 7%, which are high values. The alloy exhibits superior elongation values in addition to superior tensile strength compared to a conventional alloy.

The titanium alloy having superior mechanical properties mentioned above is desirably produced by a so-called “pre-alloy method”, in particular among powder methods, in which alloy powder obtained by powdering of alloys obtained by a melting method is used as raw material, and it is then made dense.

Here, the “pre-alloy method” means that powders which are produced using alloys which are produced by a melting method is used as a raw material for sintering, the method is opposed to mixed powder raw material in which metallic powders each consisting of a single element are separately prepared and these metallic powders are mixed.

Among the powder methods mentioned above, in particular by using the pre-alloy powder as raw material, it becomes possible to produce titanium alloy having uniform alloy composition.

Regarding desirable densifying condition in order to realize abovementioned properties, the extrusion is explained as an example, as follows.

First, titanium alloy powder and copper powder are prepared so as to yield the desired composition, they are uniformly mixed, and the mixed powder is inserted into a metallic capsule. Then, after keeping the inside of the capsule under a vacuum of not more than 10⁻¹ Torr, it is desirably pressed and formed by HIP, CIP-sintering or extrusion. It is also desirable that the powder be filled in dies and be hot-pressed in a vacuum not more than 10⁻² Torr.

Temperature (Tw) of pressing and forming while being heated is desirably in the range of (Td−100° C.)<Tw<(Td+100° C.).

As explained, the pressing and forming while being heated according to the present invention can be achieved by using a conventional method such as HIP, hot-press, CIP-HIP, or Hot-extrusion.

In the present invention, among the methods for pressing and forming while being heated, in particular in the pressing and forming by Hot-extrusion, it is desirable that the ratio of the cross-sectional area of the titanium alloy material that is to be extruded versus the cross-sectional area of the capsule that is to be inserted in the extrusion apparatus (hereinafter simply referred to as the “extrusion ratio”) be in a range of 1/10 to 1/30.

By setting the extrusion ratio in the above range, extent of flow in the capsule having titanium alloy powder inside is controlled, forge degree of the titanium alloy material that is to be extruded can be adjusted, and more preferable mechanical properties can be given.

Also the pressed and formed body by the HIP, hot pressing, or CIP-HIP can improve mechanical properties imparted to the titanium alloy material produced by forging processing by rolling, forging or the like while being heated with the abovementioned cross-sectional area ratio.

It should be noted that the capsule that covers the titanium alloy material produced by HIP, CIP-HIP, Hot-extrusion or the like is desirably removed by cutting or acid washing. The titanium alloy material from which the capsule is removed in this way can be again heated to a high temperature in a vacuum.

Since the titanium alloy material which has been processed by the treatment mentioned above has extremely superior strength, has fine crystal particles, and is strengthen by Cu which is distributed uniformly, it can be preferably used as a structural material such as in a high-strength mechanical part.

That is, not only is the strength of the titanium alloy material containing copper according to the present invention 10 to 30% higher than in a conventional titanium alloy material not containing copper, but also raw material cost can be reduced in the case in which titanium alloy scrap is used as the raw material, and as a result, cost of titanium alloy material that is the final product can be reduced 50 to 70% compared to in a conventional case.

In addition, the titanium alloy material according to the present invention exhibits high hardness value, that is, 10 to 30% higher than a material in which copper is not added.

The titanium alloy according to the present invention has the above-mentioned superior mechanical properties, and as a result, the material can be employed appropriately for medical materials in addition to industrial precision mechanical parts, and furthermore, the material can also be employed appropriately in aircraft parts to which not only strength but also abrasion resistance is required.

It should be noted that the titanium alloy containing copper can be produced by a melting method; however, there may be noticeable segregation, and it may be difficult to produce a practical alloy.

It is desirable that the titanium alloy material produced in the present invention contain at least aluminum and vanadium, and it can further contain molybdenum, iron, chromium, and/or tin in an appropriate amount. Typical alloys of these are mentioned as follows. It should be noted that the alloy that can be produced in the present invention is not limited to these, and the present invention can be employed in many kinds of other titanium alloys not shown here.

Ti-(9-10)V-(1.8-2)Fe-(2.7-3)Al-(1-10)Cu,

Ti-(13.5-15)V-(2.7-3)Cr-(2.7-3)Al-(2.7-3)Sn-(1-10)Cu,

Ti-(4.1-4.5)Al-(2.7-3)V-(1.8-2)Fe-(1.8-2)Mo-(1-10)Cu,

Ti-(4.5-5)Al-(4.5-5)V-(4.5-5)Mo-(2.7-3)Cr-(1-10)Cu,

Ti-(4.5-5)Al-(3.6-4)V-(0.5-0.6)Mo-(0.3-0.4)Fe-(1-10)Cu.

As explained so far, the present invention can provide the copper containing titanium alloy not having segregation of copper, having superior strength and hardness, and having a composition which is impossible to be produced by a conventional method. Furthermore, in the present invention, the titanium alloy can be produced more efficiently and at lower cost than in a conventional method.

EXAMPLES

Data according to Examples and Comparative Examples were collected under the following conditions.

1. Raw Material 1) 64 Alloy Powder

Production method: HDH method was applied to 64 alloy scrap and then broken and ground

Average particle diameter (d50): 52 μm

2) Copper Powder

Production method: Electrolyzed copper powder, trade name 51-N, produced by JX Nippon Mining and Metals Corporation

Average particle diameter (d50): 35 μm

3) Mixed Ratio of Copper Powder Versus Titanium Alloy Powder

1 to 10 mass %

4) Mixing

The 64 alloy powder and copper powder were uniformly mixed by a commercially available mixing apparatus.

2. Pretest

In order to determine conditions of pressing and forming while being heated, samples were made by adding each of 0%, 3%, 5%, 7%, and 10% of copper powder to 64 alloy powder, and then deformation resistance of the samples at the β transformation temperature (Td) and temperature near the β transformation temperature (Td) were observed. Measuring electric resistance by the four terminals method with increasing temperature of the test piece in an argon gas atmosphere, and a temperature at which temperature dependency of the electric resistance variation was varied was determined as the β transformation temperature (Td). As the apparatus, an electric resistance measuring apparatus (trade name: ARC-TER-1 type) was used. The results were as follows.

TABLE 1 No. Copper content (%) Td (° C.) 1 0 985 2 3 935 3 5 910 4 7 870 5 10 830

The β transformation temperature (Td) of 64 alloy (0% copper) is known to be 995° C. from a conventional document, and the test result was almost the same as the value.

Next, deformation resistance at the β transformation temperature measured above (Td), at a temperature 30° C. lower than the β transformation temperature (Td), and at a temperature 50° C. higher than the β transformation temperature (Td) were measured. The measurement was performed by a compression test using a hot processing duplicating apparatus (trade name: Thermec Master Z, produced by Fuji Electronic Industrial Co., Ltd.). The results are shown in Table 2.

TABLE 2 Copper content Td − 30° C. Td Td + 50° C. No. (%) (MPa) (MPa) (MPa) 1 0 140 95 80 2 3 180 140 120 3 5 215 185 150 4 7 300 245 180 5 10 380 310 255

3. Extrusion

Extrusion temperature was determined in consideration of extrusion force of extruding apparatus and deformation resistance of material. Each of complex powders in which copper powder was mixed to 64 alloy powder at 0%, 3%, 5%, 7% and 10% was filled in a mild steel capsule, the inside of which was evacuated to 1×10⁻² Torr, and was then sealed. Each of the powder sealed capsules was formed by Hot-extrusion as an example of pressing and forming while being heated. The temperature of heating in this process depending on copper content is shown in Table 3. Heating was performed for 2 hours. The heating temperature in each alloy containing copper and temperature difference of the temperature from the β transformation temperature (Td) are shown in Table 3.

TABLE 3 Copper content Heating temperature Difference from Td No. (%) (° C.) (° C.) 1 0 930 −55 2 3 910 −20 3 5 950 +40 4 7 930 +60 5 10 930 +100

4. Processing of Pressed and Formed Material

The capsule which was remaining on the surface of titanium alloy material produce by pressing and forming while being heated was dissolved and removed by acid washing.

5. Measurement of Mechanical Properties 1) Measurement of Tensile Strength

Tensile testing apparatus (Trade name: 5985 type, produced by Instron Corporation) was used.

2) Observation of Crystal Structure

Measuring apparatus EPMA (trade name: JXA-8100, produced by JEOL Ltd.) was used.

3) Distribution of Copper in the Crystal Structure

Measuring apparatus EPMA (trade name: JXA-8100, produced by JEOL Ltd.) was used.

Example 1 and Comparative Example 1 (Difference in Effect of Addition or No Addition of Copper Powder)

Mechanical properties in a case in which copper powder was added to 64 alloy powder and a case in which copper powder was not added were investigated. As shown in Table 4, it was confirmed that yield strength, tensile strength and hardness were superior in the case of addition of copper powder. Among copper added alloys, elongation was slightly less in the material of 5% or more copper content in particular, and it was considered that the pressing and forming temperature were influenced by being in the β temperature range.

TABLE 4 Copper Yield Tensile content strength strength Elongation Hardness No. (%) (MPa) (MPa) (%) (Hv) Example 1-1 3 1,290 1,400 7.2% 380 Example 1-2 5 1,300 1,450 3.8% 420 Example 1-3 7 1,380 1,500 3.1% 460 Example 1-4 10 1,430 1,550 2.2% 500 C. Example 1 0 1,100 1,200 8.1% 350

Example 2 and Comparative Example 2 (Difference of Temperature of Pressing and Forming)

Influence of pressing and forming temperature which is exerted on crystal structure of sintered body obtained by pressing and forming the 64 alloy in which 5% of copper was added (β transformation temperature: 950° C.) was investigated.

Mixed phase structure of the β phase and the α phase was observed in Examples 2-1 and 2-2 in which pressing and forming temperature was within the range of the present invention, as shown in FIGS. 2A and 2B. On the other hand, in Comparative Example 2-1 in which pressing and forming temperature was out of the range of the present invention, the β phase in crystal structure was coarsened. In addition, in Comparative Example 2-2, pressed and formed material could not be obtained since material became clogged in dies.

TABLE 5 Temperature of Difference Particle size of pressing and forming from Td crystal of formed No. (° C.) (° C.) body Result of evaluation Example 2-1 950 +40 55 μm Tabular structure existing inside of β particle, and α phase existing along crystal particle interface Example 2-2 880 −30 10 μm Fine α phase and β phase structure C. Example 2-1 1030 +120 225 μm  β phase coarsened C. Example 2-2 790 −120 — Material clogged in dies

Example 3 (Copper Concentration Distribution of Titanium Material Produced)

Concentration of composition in crystal structure of titanium material produced by pressing and forming in Example 2 was investigated by EPMA. Regarding Ti, Al, V, and Cu, each X-ray image was measured. These images are shown in FIGS. 3A-3D, and the results were as follows. The number shown here means count number of EPMA, and sensitivity is different in each element. Therefore, due to conversion of the count number to concentration, defining an average count number as a nominal concentration of each element, the correction coefficient of concentration was calculated as shown in Table 6. Based on this correction coefficient, existence ratio for each concentration was calculated as shown in Tables 7 and 8. The minimal concentration and the maximal concentration in each element were as follows.

Ti (Average concentration 85.5%): Minimal concentration 74.8% and maximal concentration 96.3%

Al (Average concentration 5.7%): Minimal concentration 3.8% and maximal concentration 8.6%

V (Average concentration 3.8%): Minimal concentration 3.0% and maximal concentration 4.8%

Cu (Average concentration 5.0%): Minimal concentration 2.0% and maximal concentration 8.2%

There is a region of composition almost 100% different from the nominal value of the material if observing Cu concentration from the microscopic viewpoint; however, the average value of Cu concentration in the arbitrary specified portion of 1 mm³ is always in a range from 4.5 to 5.5% no matter how the 1 mm³ part is selected, and is within ±10% versus the nominal value 5% of the material. That is, there is no segregation seen from the macroscopic viewpoint. Also, regarding Al and V, the average value of the concentration in the arbitrary specified portion 1 mm³ part was within ±8% versus the nominal value of the material in the case of Al and was within ±15% versus the nominal value of the material in the case of V.

TABLE 6 Ti Al V Cu Count of average value 2544 158 282 129 Composition of average value 85.5 5.7 3.8 5 Correction coefficient 29.8 27.7 74.2 25.8

TABLE 7 Ti Al V Cu Concentration Intensity Concentration Intensity Concentration Intensity Concentration Intensity More than 96.3 0 More than 8.6 0 More than 4.8 0 More than 8.2 0 92.7-96.3 0.3 7.6-8.6 0.1 4.6-4.8 0.1 7.6-8.2 0.2 89.2-92.7 10.1 6.7-7.6 4.2 4.4-4.6 0.7 7.1-7.6 0.8 85.6-89.2 39.6 5.7-6.7 41.9 4.3-4.4 2.8 6.5-7.1 2.8 82.0-85.6 36.9 4.8-5.7 49.6 4.1-4.3 10.7 6.0-6.5 8.1 78.4-82.0 12.7 3.8-4.8 4.1 3.9-4.1 20.8 5.4-6.0 18.7 74.8-78.4 0.4 Less than 3.8 0 3.7-3.9 29.5 4.8-5.4 27.2 Less than 74.8 0 3.5-3.7 22.7 4.3-4.8 22.8 3.3-3.5 9.6 3.7-4.3 13.4 3.2-3.3 2.6 3.1-3.7 4.4 3.0-3.2 0.4 2.6-3.1 1.2 Less than 3.0 0 2.0-2.6 0.3 Less than 2.0 0

Comparative Example 3 (Production Method of Alloy by the Raw Powder Mixing Method)

The 64 alloy containing copper powder was produced in a condition similar to Example 1, except that mixed powder in which aluminum powder (60 wt %) and vanadium powder (40%) are weighed in certain amounts and uniformly mixed was used instead of the 64 alloy powder.

There is no significant difference in mechanical properties between the 64 alloy produced and the results of Table 1 of Example 1. However, the production cost was almost double to three times compared to the material produced in Example 1. This is mainly because of difference in cost of the 64 alloy powder.

Comparative Example 4 (Alloy by Melting Method)

The 64 alloy block instead of alloy powder used in Example 1, and electrolyzed copper were prepared. The electrolyzed copper was mixed at 3, 5, and 10 wt %, and copper containing 64 alloy ingots of diameter ϕ100 each having the above corresponding copper content were obtained by using an electron beam melting furnace.

Test pieces were cut out of the copper containing 64 alloy ingots, mechanical properties thereof were investigated, and the results are shown in Table 8. Tensile strength of the ingots produced in the Comparative Example was 20% to 25% lower than the value in Example 1.

Distribution of copper in the ingot was investigated by using a CX ray micro analyzer in order to determine the cause. There was a region observed in which the Cu concentration was less than 1/10 versus the average concentration, such as being 0.3 to 0.5%, and a region was observed in which the Cu concentration was more than ten times versus the average concentration, such as being 20% to 40%, over a wide range greater than 1 mm³.

In light of the above test results, it was confirmed that the titanium alloy according to the present invention has mechanical properties superior to those of a titanium alloy produced by a conventional melting method. Furthermore, by using alloy powder produced by the pre-alloy method used in the present invention, it was confirmed that production cost can be reduced 30 to 40% even though the mechanical properties were of the same level as in the conventional raw powder mixing method.

TABLE 8 Copper Yield Tensile content strength strength Elongation Hardness No. (%) (MPa) (MPa) (%) (Hv) C. Example 4-1 3 1020 1080 5% 370 C. Example 4-2 5 1080 1140 4% 400 C. Example 4-3 10 1150 1200 3% 480

Example 4 (Cu Added 5% to Ti-10V-2Fe-3Al Alloy Powder)

Cut chips and cut powder of Ti-10V-2Fe-3Al alloy ingot was hydrogenated to produce hydrogenated product thereof, and it was crushed, ground, and sifted to obtain alloy powder of D50=50 μm. Electrolyzed copper powder used in Example 1 was added at 5% to this powder, so as to obtain mixed powder consisting of Ti-10V-2Fe-3Al alloy powder and electrolyzed copper powder. This mixed powder was charged in a mild steel capsule and was processed by Hot-extrusion. The extrusion was performed after heating for 2 hours at 800° C. Observation of structure, tensile test, hardness measurement, and EPMA observation of the extruded material were performed. The crystal particle diameter, yield strength, tensile strength, elongation, and hardness are shown in Table 9.

By X ray mapping of EPMA in a manner similar to that in Example 3, correction coefficients were calculated according to EPMA count and average concentration of each of Ti, V, Fe, Al, and Cu, and concentration distribution of each composition was measured. The results are shown in Table 10.

Comparative Example 5 (Ti-10V-2Fe-3Al Alloy Power, Copper Powder not Added)

Ti-10V-2Fe-3Al alloy powder produced in Example 4 was inserted into the mild steel capsule without mixing copper powder, and it was processed by Hot-extrusion. The extrusion conditions were the same as in Example 4. Observation of structure, tensile test, and hardness measurement of the extruded material were performed. The results are shown in Table 9.

Example 5 (Cu Powder Added 5% to Ti-15V-3Al-3Cr-3Sn Alloy Powder)

Cut chips and cut powder of a Ti-15V-3Al-3Cr-3Sn alloy ingot was hydrogenated to produce a hydrogenated product thereof, and it was crushed, ground, and sifted to obtain an alloy powder of D50=50 μm. Electrolyzed copper powder used in Example 1 was added at 5% to this powder, so as to obtain mixed powder consisting of Ti-15V-3Al-3Cr-3Sn alloy powder and electrolyzed copper powder. This mixed powder was inserted in a mild steel capsule and was processed by Hot-extrusion. The extrusion was performed after heating for 2 hours at 750° C. Observation of structure, tensile test, hardness measurement, and EPMA observation of the extruded material were performed. The crystal particle diameter, yield strength, tensile strength, elongation, and hardness are shown in Table 9.

By X-ray mapping of EPMA in a manner similar to that in Example 3, correction coefficients were calculated according to EPMA count and average concentration of each of Ti, V, Al, Cr, Sn, and Cu, and concentration distribution of each composition was measured. The results are shown in Table 11.

Comparative Example 6 (Ti-15V-3Al-3Cr-3Sn Alloy Powder, Copper Powder not Added)

The Ti-15V-3Al-3Cr-3Sn alloy powder produced in Example 5 was inserted into the mild steel capsule without mixing copper powder, and it was processed by Hot-extrusion. The extrusion conditions were the same as in Example 5. Observation of structure, tensile test, and hardness measurement of the extruded material were performed. The results are shown in Table 9.

Example 6 (Cu Powder Added 5% to Ti-4.5Al-3V-2Fe-2Mo Alloy Powder)

Cut chips and cut powder of a Ti-4.5Al-3V-2Fe-2Mo alloy ingot was hydrogenated to produce hydrogenated product thereof, and it was crushed, ground, and sifted to obtain alloy powder of D50=50 μm. Electrolyzed copper powder used in Example 1 was added at 5% to this powder, so as to obtain a mixed powder consisting of Ti-4.5Al-3V-2Fe-2Mo alloy powder and electrolyzed copper powder. This mixed powder was filled into a mild steel capsule and was processed by Hot-extrusion. The extrusion was performed after heating for 2 hours at 880° C. Observation of structure, tensile test, hardness measurement, and EPMA observation of the extruded material were performed. The crystal particle diameter, yield strength, tensile strength, elongation, and hardness are shown in Table 9.

By X-ray mapping of EPMA in a manner similar to that of Example 3, correction coefficients were calculated according to EPMA count and average concentration of each of Ti, Al, V, Fe, Mo, and Cu, and concentration distribution of each composition was measured. The results are shown in Table 12.

Comparative Example 7 (Ti-4.5Al-3V-2Fe-2Mo Alloy Powder, Copper Powder not Added)

The Ti-4.5Al-3V-2Fe-2Mo alloy powder produced in Example 6 was filled into the mild steel capsule without mixing copper powder, and it was processed by Hot-extrusion. The extrusion conditions were the same as in Example 6. Observation of structure, tensile testing, and hardness measurement of the extruded material were performed. The results are shown in Table 9.

Example 7 (Cu Powder Added 5% to Ti-5Al-5V-5Mo-3Cr Alloy Powder)

Cut chips and cut powder of a Ti-5Al-5V-5Mo-3Cr alloy ingot were hydrogenated to produce a hydrogenated product thereof, and it was crushed, ground, and sifted to obtain alloy powder of D50=50 μm. Electrolyzed copper powder used in Example 1 was added at 5% to this powder, so as to obtain a mixed powder consisting of Ti-5Al-5V-5Mo-3Cr alloy powder and electrolyzed copper powder. This mixed powder was filled into a mild steel capsule and processed by Hot-extrusion. The extrusion was performed after heating for 2 hours at 840° C. Observation of structure, tensile testing, hardness measurement, and EPMA observation of the extruded material were performed. The crystal particle diameter, yield strength, tensile strength, elongation, and hardness are shown in Table 9.

By X-ray mapping of EPMA in a manner similar to that in Example 3, correction coefficients were calculated according to EPMA count and the average concentration of each of Ti, Al, V, Fe, Mo, and Cu, and concentration distribution of each composition was measured. The results are shown in Table 13.

Comparative Example 8 (Ti-5Al-5V-5Mo-3Cr Alloy Powder, Copper Powder not Added)

Ti-5Al-5V-5Mo-3Cr alloy powder produced in Example 7 was filled into the mild steel capsule without mixing copper powder, and it was processed by Hot-extrusion. The extrusion conditions were the same as in Example 7. Observation of structure, tensile testing, and hardness measurement of the extruded material were performed. The results are shown in Table 9.

Example 8 (Cu Powder Added 5% to Ti-5Al-4V-0.6Mo-0.4Cr Alloy Powder)

Cut chips and cut powder of a Ti-5Al-4V-0.6Mo-0.4Cr alloy ingot were hydrogenated to produce a hydrogenated product thereof, and this was crushed, ground, and sifted to obtain an alloy powder of D50=50 μm. Electrolyzed copper powder used in Example 1 was added at 5% to this powder, so as to obtain mixed powder consisting of Ti-5Al-4V-0.6Mo-0.4Cr alloy powder and electrolyzed copper powder. This mixed powder was inserted in a mild steel capsule and was processed by Hot-extrusion. The extrusion was performed after heating for 2 hours at 900° C. Observation of structure, tensile testing, hardness measurement, and EPMA observation of the extruded material were performed. The crystal particle diameter, yield strength, tensile strength, elongation, and hardness are shown in Table 9.

By X-ray mapping of EPMA in a manner similar to that in Example 3, correction coefficients were calculated according to EPMA count and average concentration of each of Ti, Al, V, Mo, Cr, and Cu, and concentration distribution of each composition was measured. The results are shown in Table 14.

Comparative Example 9 (Ti-5Al-4V-0.6Mo-0.4Cr Alloy Powder, Copper Powder not Added)

Ti-5Al-4V-0.6Mo-0.4Cr alloy powder produced in Example 8 was filled into the mild steel capsule without mixing copper powder, and it was processed by Hot-extrusion. The extrusion conditions were the same as in Example 8. Observation of structure, tensile testing, and hardness measurement of the extruded material were performed. The results are shown in Table 9.

TABLE 9 Copper Yield Tensile Crystal content strength strength Elongation Hardness particle No. Alloy (%) (MPa) (MPa) (%) (Hv) diameter (μm) Example 4 Ti—10V—2Fe—3Al 5 1330 1470 9 420 20 Example 5 Ti—15V—3Al—3Cr—3Sn 5 1180 1310 10 400 20 Example 6 Ti—4.5Al—3V—2Fe—2Mo 5 1070 1200 11 360 15 Example 7 Ti—5Al—5V—5Mo—3Cr 5 1250 1350 9 450 15 Example 8 Ti—5Al—4V—0.6Mo—0.4Cr 5 980 1080 13 370 20 C. Example 5 Ti—10V—2Fe—3Al — 1200 1300 9 350 20 C. Example 6 Ti—15V—3Al—3Cr—3Sn — 1020 1100 12 330 20 C. Example 7 Ti—4.5Al—3V—2Fe—2Mo — 900 980 13 300 15 C. Example 8 Ti—5Al—5V—5Mo—3Cr — 1060 1150 9 330 15 C. Example 9 Ti—5Al—4V—0.6Mo—0.4Fe — 820 900 15 300 20

TABLE 10 Ti V Fe Al Cu Concentration Intensity Concentration Intensity Concentration Intensity Concentration Intensity Concentration Intensity More than 89.6 0 More than 13.5 0 More than 3 0 More than 3.8 0 More than 8.2 0 85.5-89.6 1.3 12.9-13.5 0.2 2.4-3   15 3.4-3.8 8 7.6-8.2 0.2 82.5-85.5 28.5 12.2-12.9 1.6 1.8-2.4 31 2.9-3.4 25 7.1-7.6 0.9 78.8-82.5 38.9 11.5-12.2 5.5 1.2-1.8 38 2.4-2.9 34 6.5-7.1 2.9 74.3-78.8 22.6 10.8-11.5 18.7 0.8-1.2 16 1.8-2.4 20 6.0-6.5 8.3 71.1-74.3 7.8 10.0-10.8 27.6 Less than 0.8 0 1.4-1.8 8 5.4-6.0 18.7 66.4-71.1 0.9  9.2-10.0 27.8 0.9-1.4 5 4.8-5.4 26.8 Less than 66.4 0 8.4-9.2 14.2 Less than 0.9 0 4.3-4.8 23.5 7.6-8.4 3.6 3.7-4.3 13.1 7.0-7.6 0.6 3.1-3.7 4.4 6.4-7.0 0.2 2.6-3.1 1.1 Less than 6.4 0 2.0-2.6 0.1 Less than 2.0 0

TABLE 11 V Al Cr Sn Cu Ti Concen- Concen- Concen- Concen- Concen- Concentration Intensity tration Intensity tration Intensity tration Intensity tration Intensity tration Intensity More than 81.6 0 More than 0 More than 0 More than 0 More than 0 More than 0 17.9 3.8 3.8 3.8 3.8 78.5-81.6 1.1 17.1-17.9 0.2 3.4-3.8 8 3.4-3.8 7 3.4-3.8 5 7.6-8.2 0.2 74.1-78.5 28.7 16.5-17.1 1.6 3.1-3.4 28 3.1-3.4 25 3.1-3.4 28 7.1-7.6 0.9 70.3-74.1 38.7 15.9-16.5 5.5 2.7-3.1 33 2.7-3.1 34 2.7-3.1 36 6.5-7.1 2.9 67.1-70.3 22.3 15.2-15.9 18.7 2.2-2.7 18 2.2-2.7 21 2.2-2.7 22 6.0-6.5 8.3 63.9-67.1 8.3 14.5-15.2 27.6 1.8-2.2 9 1.8-2.2 9 1.8-2.2 7 5.4-6.0 19.2 59.9-63.9 0.9 13.9-14.5 27.8 1.5-1.8 4 1.5-1.8 4 1.5-1.8 2 4.8-5.4 26.8 Less than 59.9 0 13.2-13.9 14.2 Less than 0 Less than 0 Less than 0 4.3-4.8 23.5 1.5 1.5 1.5 12.4-13.2 3.6 3.7-4.3 13.3 11.7-12.4 0.6 3.1-3.7 4.5 11.1-11.7 0.2 2.6-3.1 0.3 Less than 0 2.0-2.6 0.1 11.1 Less than 2.0 0

TABLE 12 Ti Al V Fe Mo Cu Concen- Concen- Concen- Concen- Concen- Concen- tration Intensity tration Intensity tration Intensity tration Intensity tration Intensity tration Intensity More than 0 More than 0 More than 0 More than 0 More than 0 More than 0 88.5 3.8 3.6 2.5 2.5 8.2 84.3-88.5 1.1 3.5-3.8 7 3.5-3.6 7 2.2-2.5 10 2.3-2.5 3 7.6-8.2 0.2 80.2-84.3 28.7 3.1-3.5 27 3.3-3.5 28 1.9-2.2 32 2.1-2.3 28 7.1-7.6 0.9 76.4-80.2 38.7 2.7-3.1 33 3.2-3.3 34 1.6-1.9 38 1.9-2.1 36 6.5-7.1 3.1 72.5-76.4 22.3 2.4-2.7 19 3.1-3.2 19 1.3-1.6 20 1.7-1.9 23 6.0-6.5 8.5 69.0-72.5 8.3 2.1-2.4 10 3.0-3.1 9 Less than 1.3 0 1.5-1.7 8 5.4-6.0 19.2 65.5-69.0 0.9 1.8-2.1 4 2.8-3.0 3 1.3-1.5 2 4.8-5.4 26.4 Less than 0 Less than 0 2.7-2.8 0 Less than 0 4.3-4.8 23.3 65.5 1.8 1.3 2.5-2.7 3.7-4.3 13.4 2.4-2.5 3.1-3.7 4.5 2.2-2.4 2.6-3.1 0.4 Less than 2.2 2.0-2.6 0.1 Less than 2.0 0

TABLE 13 Ti Al V Mo Cr Cu Concen- Concen- Concen- Concen- Concen- Concen- tration Intensity tration Intensity tration Intensity tration Intensity tration Intensity tration Intensity More than 0 More than 0 More than 0 More than 0 More than 0 More than 0 95.5 6.1 5.9 5.7 3.8 8.2 91.3-95.5 0.8 5.6-6.1 7 5.7-5.9 0.3 5.3-5.7 3 3.4-3.8 6 7.6-8.2 0.2 87.5-91.3 22.4 5.1-5.6 27 5.5-5.7 1.6 4.9-5.3 28 3.1-3.4 25 7.1-7.6 1.1 83.9-87.5 40.4 4.6-5.1 33 5.3-5.5 5.5 4.4-4.9 34 2.7-3.1 33 6.5-7.1 2.9 80.1-83.9 26.2 4.1-4.6 18 5.1-5.3 18.7 4.1-4.4 23 2.2-2.7 22 6.0-6.5 8.3 76.6-80.1 9.1 3.6-4.1 10 4.9-5.1 27.6 3.7-4.1 9 1.8-2.2 11 5.4-6.0 18.7 73.1-76.6 1.1 3.1-3.6 5 4.7-4.9 27.3 3.3-3.7 3 1.5-1.8 3 4.8-5.4 26.4 Less than 0 Less than 0 4.5-4.7 14.4 Less than 3.3 0 Less than 1.5 0 4.3-4.8 23.5 73.1 3.1 4.2-4.5 3.6 3.7-4.3 13.5 4.0-4.2 0.7 3.1-3.7 4.9 3.7-4.0 0.3 2.6-3.1 0.4 Less than 0 2.0-2.6 0.1 3.7 Less than 2.0 0

TABLE 14 Ti Al V Mo Fe Cu Concen- Concen- Concen- Concen- Concen- Concen- tration Intensity tration Intensity tration Intensity tration Intensity tration Intensity tration Intensity More than 0 More than 0 More than 0 More than 0 More than 0 More than 0 97.1 6.1 5.0 1.3 1.0 8.2 93.7-97.1 1.1 5.6-6.1 8 4.8-5.0 0.4 1.1-1.3 3 0.8-1.0 13 7.6-8.2 0.2 90.2-93.7 22.2 5.1-5.6 26 4.6-4.8 1.6 1.0-1.1 26 0.6-0.8 31 7.1-7.6 1.4 86.5-90.2 40.1 4.6-5.1 32 4.4-4.6 5.4 0.8-1.0 36 0.4-0.6 39 6.5-7.1 3.7 82.7-86.5 26.5 4.1-4.6 18 4.2-4.4 18.3 0.7-0.8 24 0.2-0.4 17 6.0-6.5 8.3 79.1-82.7 9.2 3.6-4.1 11 4.0-4.2 27.9 0.5-0.7 9 Less than 0.2 0 5.4-6.0 17.9 75.3-79.1 0.9 3.1-3.6 5 3.8-4.0 27.2 0.4-0.5 2 4.8-5.4 26.6 Less than 0 Less than 0 3.6-3.8 14.4 Less than 0.4 0 4.3-4.8 22.8 75.3 3.1 3.4-3.6 3.6 3.7-4.3 13.5 3.2-3.4 0.8 3.1-3.7 4.9 3.0-3.2 0.4 2.6-3.1 0.6 Less than 3.0 0 2.0-2.6 0.1 Less than 0 2.0

The present invention relates to titanium alloy produced by a powder method and to a method for production thereof. In the present invention, strong and hard titanium alloy containing copper in high concentration, which has been difficult to produce by a conventional method, and having no segregation of copper, can be produced at lower cost than in a conventional method. 

1. A method for production of α+β type titanium alloy, the method comprising steps of: titanium alloy powder is produced from raw titanium alloy, and the titanium alloy contains at least aluminum and vanadium and further contains at least one selected from molybdenum, iron, chromium, and tin, and 1 to 10 mass % of copper powder and the titanium alloy powder are pressed and formed while being heated so as to form a dense compact.
 2. The method for production of α+β type titanium alloy according to claim 1, wherein a temperature in the pressing and forming while being heated (Tw(° C.)) is in the following range: (Td−100° C.)<Tw<(Td+100° C.) Td(° C.) being β transformation temperature of the titanium alloy that is pressed and formed.
 3. The method for production of α+β type titanium alloy according to claim 1, wherein size of a crystal phase consisting particles not greater than 100 μm, and the copper concentration per 1 mm³ of an arbitrary specified portion in the crystal phase is within ±40% compared to another arbitrary specified portion.
 4. The method for production of α+β type titanium alloy according to claim 1, wherein the titanium alloy comprises titanium, 9-10 mass % vanadium, 1.8-2 mass % iron, 2.7-3 mass % aluminum and 1-10 mass % copper.
 5. The method for production of α+β type titanium alloy according to claim 1, wherein the titanium alloy comprises titanium, 13.5-15 mass % vanadium, 2.7-3 mass % chromium, 2.7-3 mass % aluminum, 2.7-3 mass % tin and 1-10 mass % copper.
 6. The method for production of α+β type titanium alloy according to claim 1, wherein the titanium alloy comprises titanium, 4.1-4.5 mass % aluminum, 2.7-3 mass % vanadium, 1.8-2 mass % iron, 1.8-2 mass % molybdenum and 1-10 mass % copper.
 7. The method for production of α+β type titanium alloy according to claim 1, wherein the titanium alloy comprises titanium, 4.5-5 mass % aluminum, 4.5-5 mass % vanadium, 4.5-5 mass % molybdenum, 2.7-3 mass % chromium and 1-10 mass % copper.
 8. The method for production of α+β type titanium alloy according to claim 1, wherein the titanium alloy comprises titanium, 4.5-5 mass % aluminum, 3.6-4 mass % vanadium, 0.5-0.6 mass % molybdenum, 0.3-0.4 mass % iron and 1-10 mass % copper.
 9. The method for production of α+β type titanium alloy according to claim 1, wherein the copper concentration per 1 mm³ of an arbitrary specified portion in the crystal phase is within ±10% compared to average concentration of the α+β type titanium alloy.
 10. The method for production of α+β type titanium alloy according to claim 1, wherein the copper contained in a range of 3 to 10 mass %. 